1. Field of the Invention
The invention is directed to a clutch release arrangement, particularly for a clutch in a motor vehicle, including a master cylinder for a hydraulic system, a pedal for actuating the master cylinder to disengage the clutch, and an articulated energy accumulator which stores energy when the clutch is engaged and provides a boosting force which reduces the actuating force when the clutch is disengaged.
2. Description of the Related Art
Release arrangements of this type are frequently used in modern hydraulically actuated clutches and are known from practice. The energy accumulator has a spring which holds the pedal in its basic position or at least reinforces a force holding the pedal. When the pedal is depressed, the spring is pretensioned slightly. In so doing, the spring swivels until its point of application of force at the pedal goes beyond a dead center and reinforces the movements of the pedal by an added force on the pedal path following the dead center. This enables a reduction in the force expended when depressing the pedal, at least along the path following the top dead center, where the energy accumulator adds its energy as a boosting force to the pedal force.
Due to the articulation of the energy accumulator at the pedal, in particular as an over-center spring, the pedal force on the second half of the pedal path can be noticeably reduced in order to be able to overcome more easily the spring acting in the clutch of the motor vehicle, particularly at the end of the pedal path. However, known kinematic couplings of energy accumulators with a clutch pedal have shown themselves to be in need of improvement for certain applications. Above all, it is disadvantageous that the path of the force reinforcing the pedal force can not only be adjusted in height with sufficient accuracy, the variability of the reinforcement force along the pedal path can also not be adapted to the requirements of the pedal force on the pedal path. For example, when the maximum force should be further reduced, this can only be done in the known solution by increasing the force for depressing the pedal.
The invention provides an over-center kinematic arrangement which makes it possible to adapt a boosting force of an energy accumulator to the required curve of a pedal force, wherein the pedal force should also be smaller when the operator steps on the pedal and the produced force should be substantially greater in the area of the boosting force acting through the energy accumulator after passing a dead center point.
According to the invention, a kinematic arrangement between the energy accumulator and the pedal has a high degree of variability with respect to the curve of the boosting force and capable of being set to the force requirements of the clutch of any defined type of motor vehicle without changing the type of kinematics.
It is suggested that the kinematic arrangement is formed of two levers which can be arranged in the motor vehicle in a variable manner. The first lever is constructed as a swivel lever and is mounted to the chassis of the motor vehicle in an articulated manner. Accordingly, together with the end of the energy accumulator, it forms a joint at which the second lever, namely, the transmission lever for the pedal, is likewise arranged in an articulated manner and connects an arm of the pedal to the energy accumulator in an articulated manner. Aside from the lever lengths which are adapted first of all to the given structural conditions of the motor vehicle, the main parameter is the relative angular position of the two levers with respect to one another which influences the boosting force in the area following the dead center. When the selected angle is smaller, there is a greater boosting force in the area following the dead center. It will be seen that only the articulation of the cam follower at the chassis needs to be changed in order to achieve the desired adjustment of the boosting force through the energy accumulator when the pedal is actuated.
In this connection, it is assumed that the energy accumulator is arranged at the chassis so as to be swivelable and approximately forms a line with the transmission lever and the arm of the pedal up to a pedal bearing. A certain obtuse angle is advisably arranged between the three elements to form a stable rest position of the pedal. When the pedal is depressed, the angles reach 180xc2x0 and, therefore, the kinematic dead center. The faster the angles change beyond this value subsequently, the higher the boosting force for the pedal, provided that the spring force available in the energy accumulator acts along the required path to adequate height.
A second modification of the kinematic arrangement described above includes only one lever which connects the chassis to the end of the energy accumulator in an articulated manner but has a rolling cam on which a roller can run, this roller being arranged at the arm of the pedal. The lever acting as cam follower is pressed against the roller at the arm by the spring force of the energy accumulator and forms a stable system when the arm approximately forms a line with the acting boosting force. As in the example mentioned above, a certain angle is provided at the rolling cam in order to stabilize the kinematics in the basic position of the pedal; this angle must first be overcome when depressing the pedal to dead center. After this dead center is overcome, the roller runs along the rolling cam and undergoes a component of the boosting force by means of the energy accumulator, which component increases as the angle of the path normal of the roller to a center axis of the arm increases. It will be seen that the proposed kinematic arrangement make it possible to adapt the curve of the boosting force for the pedal force to the requirements of the system at any point along the path of the pedal. Apart from the variability of the design of the rolling cam, the location for arranging the cam follower at the chassis is also changed, which provides additional possibilities for adapting to the requirements of the curve of the pedal force.
Another suggestion which is based on the principle of the design of a rolling cam cooperating with the energy accumulator consists in replacing the conventional energy accumulator with a simplified construction of an energy accumulator. The simplified construction includes a leg spring having one end in the chassis and another end with a roller which communicates with a rolling cam arranged at the pedal. When the pedal is actuated, the roller rolls along the cam and generates a force component which supports the actuating force of the pedal as a moment about the pedal bearing in the rotating direction of the pedal. It will also be seen in this case that the rolling cam can be optionally selected and provides a boosting force serving to adapt the pedal forces in an optimal manner for every angular position of the pedal.
The invention allows for numerous embodiment forms, some of which are shown in the drawings and are described below in order to further illustrate its basic principle.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.